The present invention relates to a fastening device particularly for sports shoes and particularly for ski boots or skates.
Numerous levers used in ski boots are currently known; for this purpose, Italian Patent no. 1039897 discloses a lever constituted by an arm which is pivoted at one end, by means of an appropriate pivot, to two shoulders which are rigidly coupled to a flap of the boot; the arm has a toothed region for interaction with the end of a hook that can be associated, at its other end, with the other flap of the boot to be closed.
This known lever must have a surface finish that is aesthetically adequate, because it is visible on the boot; this accordingly entails the use of materials, such as aluminum or plastics, that have an attractive outward appearance for the skier, but such materials do not have the high-level strength characteristics required to withstand the stresses and impacts to which they are subjected during sports practice.
In any case, the protrusion of the levers with respect to the lateral surface of the boot does not give said boot a clean aesthetic appearance, as said levers tend to accidentally open or break in case of impact with the snow-covered piste or with the slalom pole or with the other boot.
The lever is furthermore subjected to loads when closed, and this increases the possibility of breakage.
As a partial solution to these drawbacks, Italian Patent 1054289 discloses a closure assembly for ski boots which, despite using a simplified structure, has been found to be difficult to close due to the limited hand resting surface to which the closing effort must subsequently be applied.
Italian patent no. 1,082,434 is also known which discloses a lever device for closing a ski boot; said device comprises a toothed band, which is rigidly coupled to a flap of the upper, and a lever, which is rigidly coupled to the other flap of the upper and has a ratchet-like advancement system which cooperates with the toothed band so as to close the boot.
This solution allows to increase the degree of tension of the toothed band while maintaining the previously achieved degree of fastening, but at the same time it has other drawbacks which are due essentially to its structural complexity and to the difficulty in operating it, because it is necessary to place the tip of the lever, which is pivoted at the end of the lever, at the interspace between two adjacent teeth of the band, so that jamming does not occur during the closure of the lever; in order to obviate this drawback, it is necessary to perform several movements with very limited take-ups.
The tip of the lever furthermore has a central recess that forms two lateral tabs which are the only part that interacts with the teeth of the underlying band: this configuration, which is necessary to avoid interacting with the lever produces further drawbacks due to the possibility of deforming said tabs, consequently making it impossible to adjust the closure.
In any case, the lever still protrudes vertically with respect to the band and thus to the flap of the upper; furthermore, the possible forming of ice or the accumulation of snow at the lever can make said lever disengage from the toothed band in case of accidental impacts, thus causing the device to open.
Italian Utility Model patent no. 185645 filed on Jan. 20, 1981 discloses a lever closure system, particularly for motorcycling boots, in which the arm of the lever, which is again pivoted at one end at a suitable support that is rigidly coupled to one flap, is inserted within suitable notches provided on another flap to be closed.
Even this solution, while having a limited number of components, has some drawbacks, such as the direct interaction of the lever arm with the flap to be closed, which entails breakages or deformations due to the different strength of the materials that are in mutual contact.
French patent, published as no. 2432280 and filed on Aug. 3, 1978 discloses a closure device which is again constituted by a U-shaped lever arm the wings of which are again pivoted, at their ends, at a suitable support which is rigidly coupled to a flap; a pivot is interposed between said wings and interacts with a suitable rack that is obtained from the other flap to be joined and protrudes from it.
This solution has drawbacks owing to the fact that the engagement between the lever arm and the rack is not always reliable, because the rack must necessarily be made of plastics, together with the flap of the boot, and therefore be made of a material that does not withstand the intense stresses applied while skiing.
Among the various described situations, the same Applicant of the above mentioned French patent in fact provides for the use of an individual lever arm which has a toothed region that interacts with an adapted pivot which is associated transversely with respect to the wings of a U-shaped bar which is pivoted to the other flap to be joined so that said bar can oscillate about one edge.
Even this solution therefore has the drawbacks described above, which it combines with a difficult closing operation for the skier, who must make the lever arm rotate practically through 180.degree..
As a partial solution to this drawback, Italian Utility Model no. 182322 discloses a closure device particularly for ski boots in which there is a lever arm that is pivoted, at one end, at one of the flaps to be fastened; the end of a traction element is articulated to a median portion of said lever element, and said traction element has, at its opposite end, a hook-like element which can be coupled in an engagement seat provided at the other flap to be fastened; said traction element has means for adjusting its useful length and has at least one substantially flexible portion.
Even this solution, however, constructively includes a large number of components and furthermore protrudes beyond the profile of the boot; the closure device is furthermore considerably elongated along its longitudinal axis, which affects a very large region of the boot.
As a partial solution to these drawbacks, Japanese Patent application no. 3-318673 of Nov. 7, 1991 discloses a lever for sports shoes, particularly for boot,, the particularity of which is the fact that it comprises a lever arm which is totally or partially associated or associable at at least one suitable seat formed on one of said flaps; at least one grip element for engagement means provided on said lever arm is associated on the other one of said flaps.
Although it is undoubtedly valid, even this described solution has drawbacks, because it has been found that the connection between the lever arm and the seat formed on the flaps is not optimum; moreover, it has been found that it is necessary to modify the setting of the degree of tension that can be applied with the lever.
Therefore, the several drawbacks that have been observed in the described prior art include the provision of levers which are subjected to loads once fastening has occurred and thus after closing said lever, and the provision of levers which occupy a considerable bulk, especially in a vertical direction.